Have you installed any mods at all? Are you using the A10 sim-mod? If you are then you maye have installed them in the incorrect order or the download was corrupt. Lockon can be very temperamental and the slightest thing can give you white model textures. This is normally only fixed by a fresh install of lockon.
Have a read of Polecats 20 step lockon install with mods at the 104th Phoenix forum here http://www.104thphoenix.com/modules.php?name=Forums&file=viewtopic&t=1089
If you follow this you should have no trouble. Hope this helps
S!